<!DOCTYPE html>
<html >
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>自定义右键菜单</title>
    <style type="text/css">
        body,
        ul,
        li {
            margin: 0;
            padding: 0;
        }

        body {
            font: 12px/24px arial;
        }

        #menu {
            position: absolute;
            top: 0px;
            left: 0px;
            width: 100px;
            border-radius: 3px;
            list-style-type: none;
            border: 1px solid #8f8f8f;
            padding: 2px;
            background: #fff;
            display: none;
        }
        #menu.show{
            display: block;
        }

        #menu li {
            position: relative;
            height: 24px;
            padding-left: 24px;
            background: #eaead7;
            vertical-align: top;
        }

        #menu li a {
            display: block;
            color: #333;
            background: #fff;
            padding-left: 5px;
            text-decoration: none;
        }

        #menu li.active {
            background: #999;
        }

        #menu li.active a {
            color: #fff;
            background: #8f8f8f;
        }
        #menu li:hover{
            background: #999;
        }
        #menu li:hover a {
            color: #fff;
            background: #8f8f8f;
        }

        #menu li em {
            position: absolute;
            top: 0;
            left: 0;
            width: 24px;
            height: 24px;
            background: url(http://www.fgm.cc/learn/lesson5/img/ico.png) no-repeat;
        }

        #menu li em.cur {
            background-position: 0 0;
        }

        #menu li em.copy {
            background-position: 0 -24px;
        }

        #menu li em.paste {
            background-position: 0 -48px;
        }
    </style>
    <script type="text/javascript">
        // window.onload = function () {
        //     var oMenu = document.getElementById("menu");
        //     var aLi = oMenu.getElementsByTagName("li");
        //     //加载后隐藏自定义右键菜单
        //     oMenu.style.display = "none";
        //     //菜单鼠标移入/移出样式
        //     for (i = 0; i < aLi.length; i++) {
        //         //鼠标移入样式
        //         aLi[i].onmouseover = function () {
        //             this.className = "active"
        //         };
        //         //鼠标移出样式
        //         aLi[i].onmouseout = function () {
        //             this.className = ""
        //         }
        //     }
        //     //自定义菜单
        //     document.oncontextmenu = function (event) {
        //         var event = event || window.event;
        //         var style = oMenu.style;
        //         style.display = "block";
        //         style.top = event.clientY + "px";
        //         style.left = event.clientX + "px";
        //         return false;
        //     };
        //     //页面点击后自定义菜单消失
        //     document.onclick = function () {
        //         oMenu.style.display = "none"
        //     }
        // };
    </script>
</head>

<body>
    <center>自定义右键菜单，请在页面点击右键查看效果。</center>
    <ul id="menu">
        <li><em class="cut"></em><a href="javascript:;">剪切</a></li>
        <li><em class="copy"></em><a href="javascript:;">复制</a></li>
        <li><em class="paste"></em><a href="javascript:;">粘贴</a></li>
    </ul>
    <script>
        var menuEle = document.getElementById("menu")
        document.oncontextmenu = function(e){
            e.preventDefault()
            const left = e.x
            const top = e.y
            const style = `top:${top}px;left:${left}px;`
            menuEle.classList.add('show')
            console.log(style)
            menuEle.style.cssText  = style
        }
        document.addEventListener('click',function(){
            menuEle.classList.remove('show')
        })
        window.onkeydown = function(e){
            if(e.code === "KeyC" && e.ctrlKey){
                e.preventDefault()
            }        
        }
    </script>
</body>

</html>